(View this on Windows or using the Windows Times New Roman TrueType font to see the bug. Otherwise, change the size of the DIV so that the first line ends exactly at the end of the first SPAN.)
For some reason, the trailing space character increases the line-height of the next line. Maybe it has lost its baseline and is positioned vertical-align:bottom? Or is the wrong font-size? Who knows.
However, this causes the gap between the second and third lines to be bigger than expected.